At first I thought it was a straw caught up in the rear trim and I tugged on it a bit before crawling underneath to have a look... glad I didn’t pull it off because it’s clearly attached. Perhaps it just needs to be cut to level with the trim.

Yes it’s the overflow for those very rare times when you somehow slightly overflow your tank. Seems to me if the fuel nozzle didn’t turn off on its own when filling, this little tube would do nothing and you would have fuel all over the side of your car anyways.

Oh well... other than looking odd it’s not hurting anything.

Only visible on some Velars so others must have shorter overflow tubes.